The present invention relates to a calcium carbonate powder in a platelet-like particulate form and a method for the preparation thereof. More particularly, the invention relates to a powder of calcium carbonate of which each of the particles has a flat platelet-like configuration and a method for the preparation of such a powder of calcium carbonate by the synthetic method of the carbonation of a milk of lime.
Needless to say, the demand for natural and synthetic calcium carbonate powders is rapidly growing in recent years in various fields of industry including paper making, processing of rubbers and plastics, preparation of inks, paints and many other useful products by virtue of the excellent whiteness as a pigment and reinforcing effect as a filler to impart mechanical strengths and abrasion resistance to the above named materials.
As is known, powders of synthetic calcium carbonate are usually prepared by introducing carbon dioxide gas into a milk of lime to effect the reaction of calcium hydroxide and carbon dioxide precipitating calcium carbonate in a powdery form. The particulate configuration of the calcium carbonate powder obtained in such a method of carbonation of a milk of lime is usually spindle-like, cube-like or needle-like. Presumably this is the reason for the inferiority of conventional calcium carbonate powders in connection with the smoothness and luster of the surface and the mechanical strengths of the materials impregnated with the powder as a pigment or filler in comparison with kaolin clay, mica and other inorganic powders having a platelet-like particuLate configuration although calcium carbonate powders are preferred when in high whiteness and large ink absorption are desired. Accordingly, the application fields of the conventional calcium carbonate powders are under considerable limitations in this regard.